At the most basic level, almost every human has one thing on his or her mind: Survival. We are all constantly trying to protect ourselves. Whether it's locking car doors while driving through an unfamiliar area, applying bug repellant or just not talking to strangers, we anticipate threats and form barriers against the unknown.
The unknown can be scary -- like entering a dark room, it can make your imagination run wild. The possible scenarios that run across the mind can lead to some innovative thoughts. From a boulder placed strategically in front of a cave's entrance to a moat surrounding a castle, people have come up with an unending supply of creative security ideas throughout history. These ideas have all hinged on keeping bad things out or keeping sinister individuals in (i.e. prison). While our wants of today may
differ from our ancestors, our needs are essentially the same.